2023-01-24 11:32:50

by Alexander Potapenko

Subject: [PATCH] btrfs: zlib: zero-initialize zlib workspace

KMSAN reports uses of uninitialized memory in zlib's longest_match()
called on memory originating from zlib_alloc_workspace().
This issue is known by zlib maintainers and is claimed to be harmless,
but to be on the safe side we'd better initialize the memory.

Link: https://zlib.net/zlib_faq.html#faq36
Reported-by: [email protected]
Signed-off-by: Alexander Potapenko <[email protected]>
---
fs/btrfs/zlib.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/btrfs/zlib.c b/fs/btrfs/zlib.c
index 01a13de118320..da7bb9187b68a 100644
--- a/fs/btrfs/zlib.c
+++ b/fs/btrfs/zlib.c
@@ -63,7 +63,7 @@ struct list_head *zlib_alloc_workspace(unsigned int level)

workspacesize = max(zlib_deflate_workspacesize(MAX_WBITS, MAX_MEM_LEVEL),
zlib_inflate_workspacesize());
- workspace->strm.workspace = kvmalloc(workspacesize, GFP_KERNEL);
+ workspace->strm.workspace = kvzalloc(workspacesize, GFP_KERNEL);
workspace->level = level;
workspace->buf = NULL;
/*
--
2.39.0.246.g2a6d74b583-goog

2023-01-24 17:07:02

by David Sterba

Subject: Re: [PATCH] btrfs: zlib: zero-initialize zlib workspace

On Tue, Jan 24, 2023 at 12:32:34PM +0100, Alexander Potapenko wrote:
> KMSAN reports uses of uninitialized memory in zlib's longest_match()
> called on memory originating from zlib_alloc_workspace().
> This issue is known by zlib maintainers and is claimed to be harmless,
> but to be on the safe side we'd better initialize the memory.
>
> Link: https://zlib.net/zlib_faq.html#faq36
> Reported-by: [email protected]
> Signed-off-by: Alexander Potapenko <[email protected]>

Added to misc-next, thanks.